If using a chargrill, preheat it to ensure it is very hot before cooking.
Peel and dice the potatoes. Place in a pan of cold water, add the salt and bring to the boil. Once boiling reduce the heat to a simmer and cook the potatoes until tender.
In a separate pan warm the cream, milk and butter until the butter has melted.
When the potatoes are cooked, drain and then mash. Add half of the cream, milk and butter and stir with a wooden spoon until smooth. Add more of the milk mixture if required. Season with the black pepper and more salt if required.
Season the lamb steaks with salt and black pepper and a drizzle of olive oil. Chargrill each side for 3 minutes, turning the steak through 90 degrees to achieve a criss cross marking.
To make the saucePick the leaves from the parsley and mint and discard the stalks. Chop both herbs finely and mix together in a bowl.
Finely dice the garlic and add to the herbs with the mustard and olive oil. Finally add the capers and stir to mix the mustard and olive oil together. Squeeze in the juice of the lemon and check the seasoning. Add salt if required.
For the cabbageQuarter the cabbage and remove the tough stalk. Peel and finely the dice the garlic.
Slice very finely. In a wide bottomed pan, melt the butter and add the cabbage, the garlic and the seasoning. Put a tight fitting lid on the pan, add a splash of water, increase the heat and cook the cabbage for 5 minutes until the cabbage is tender. Check the seasoning and keep warm.
To serveRe-heat the cabbage and ensure that the mashed potatoes are hot. Spoon a generous amount of mash onto a plate, place the cabbage alongside and then the lamb on top. Finish the dish with the herby sauce and serve immediately.